Process of reacting dioxane or piperazine with certain active methyl-substituted quaternized heterocyclic bases



PROCESS OF REACTINC DIOXANE OR PIPERAZINE 4, 1 G N WHITE 2,825,731

WITH CERTAIN ACTIVE METHYL-SUBSTITUTED QUATERNIZED I-IETEROCYCLIC BASESFiled June 21, 1955 Inventor GERALD NOEL WHITE Attorneys i nite PROCESSOF REACTING DIOXANE R PIPERA- ZINE WITH (IERTAIN ACTIVE METHYL-SUB-STIgIEUTED QUATERNIZED HETEROCYCLIC BA S Gerald Noel White, Carshalton,England, assignor to Photo-Chemical Company Limited, London, England, aBritish company This invention is concerned with improvements in orrelating to photographic sensitizers for use in the production of silverhalide emulsions for photography.

Many sensitizers for silver halide emulsions are. known which contain asessential features of their molecular structure two heterocyclicresidues linked together by a carbon chain through conjugated methinegroups contained in the heterocyclic residues, each heterocyclic residuecontaining a tertiary nitrogen atom adjacent or in the para position toa methylene substituted methine group, one of the tertiary nitrogenatoms being quaterm'zed and the methylene substituents forming theterminal groups of the carbon chain. .Such sensitizers are prepared bythe quaternization of compounds containing heterocyclic rings of theabove type, that is rings containing a tertiary nitrogen atom adjacentor in the para position' to a methyl substituted methine group, followedby condensation with a suitable derivative of the residue which is toform the carbon chain. On quaternization this tertiary nitrogen atombecomes positively charged and the electron displacement taking placetowards it weakens the attraction between the carbon and hydrogen atomsof the methyl group. The result of quaternization, therefore, is to makethis methyl group no longer a reacting entity but liable instead toundergo proton release in the presence of any reagent that is protonaccepting.

Hitherto such sensitizers have been prepared by condensing a quaternizedheterocyclic compound. of the above type with a carbon chain compoundcarrying terminal groups capable of being eliminated, on protonacceptance, as water, hydrogen sulphide, mercaptans,

'aryl primary bases or alcohols, the choice of compound that providesthe carbon chain being dependent on whether the two heterocyclicresidues to be linked are similar or dissimilar or whether the carbonchain that links them is to be long or short, linear or branched.

A disadvantage of many of the sensitizers of this type previouslyproposed has been that the carbon chain compounds used for thecondensation have themselves been difiicult to prepare and expensive.

I have now developed a novel range of photographic sens'itizers havingvaluable sensitization characteristics in which the compounds used inthe condensation to link the two heterocyclic residues are in'generalboth cheap and readily available.

In order to facilitate recognition of my new compounds, I now give theoptical characteristics of six compounds according to the invention, thepreparation of which will 'be described hereinafter. The opticalcharacteristics are shown in the accompanying drawing in which the sixfigures show curves obtained by plotting density, that is the logarithmof the reciprocal transmission (ratio of transmitted light to incidentlight) as ordinates against the wavelength of the incident light asabscissae, for each of the six compounds in question. In all cases thecurves were obtained using a concentra- States Patent "ice tion of 1 mg.of sensitizer per 100 ccs. of photographic emulsion; the units ofwavelength are hundreds of Angstrom units.

In common with many other quaternary salts, the compounds of the presentinvention decompose at high temperatures, the actual temperature ofdecomposition in any given case depending on the rate of heating,crystal size, etc.; a temperature of decomposition for a particularcompound is therefore to a large extent irreproducible. In thesecircumstances a statement of the temperatures of decomposition of thecompounds is virtually worthless and will not be given in the examplesto be set forth hereinafter.

I have further found that the new sensitizers can be prepared byquaternizing a suitable heterocyclic compound and condensing thequaternary salt obtained with an alicyclic diether or an alicyclicdi-imine.

According to a feature of the present invention, therefore, I provide aprocess for the preparation of the new sensitizers, in which aquaternized heterocyclic base containing nitrogen in the ring and amethyl substituted methine group adjacent or in the para position to thenitrogen atom of the base is condensed with an alicyclic diether or analicyclic di-imine.

The quaternized base to be used in the process according to theinvention is preferably a quaternary salt of the general formula where Rand R which may be the same or difierent, are alkyl, aryl or aralkylgroups or together form part of a hydrocarbon ring, which itself may besubstituted or unsubstituted; R is an alkyl group; Y is an oxygen,sulphur or selenium atom or a substituted or unsubstituted methylene orimino group and X- is an anion.

It is preferred that R and R together form part of a substituted orunsubstituted benzene ring, preferred substituents in the benzene ringbeing alkyl, aryl, aralkyl and alkoxy groups and halogen atoms; R is anethyl group; Y is an oxygen or sulphur atom, and X- is a chloride,bromide, iodide, thiocyanate perchlorate, nitrate or sulphate ion. Thecondensation is preferably carried out in the presence of a dehydratingagent and/or an acid binding agent.

A suitable alicyclic diether for use in the process according to theinvention is, for example, dioxan and a suitable alicyclic di-imine is,for example, piperazine.

The condensation reaction is, in general, slow and is advantageouslycarried out at elevated temperatures, for example, at the boiling pointof the reaction mixture. Even at elevated temperatures the reaction maytake several hours, or in certain cases even two to three days, to reacha maximal yield which can, in general, only be determined by trial anderror, that is trial reactions should be carried out using a particularset of reaction conditions and the optimum time for the reaction beingdetermined by finding the time required to give the maximum yield. 7

Suitable dehydrating agents for use in the process ac cording to theinvention are, for example, aliphatic acid anhydrides, such as aceticanhydride and propionic anhydride. Tertiary amines, such for example aspyridine, collidine and isoquinoline, are suitable acid binding agentsfor use in the condensation reaction. In general it may hcsaid thatreaction conditionsapplicable to condensa tion reactions in general areequally applicable to the condensation reaction according to theinvention, and therefore that suitable dehydrating agents, acid bindingagents, temperatures of reaction and other reaction conditions will beapparent to those skilled in ,the art.

The proportions of the various reactants and the conditions of thecondensation should therefore be adiusted to'suit the properties of thesensitizer obtained and the kinetics of its production. For example theproportions of alicyclic diether or alicyclic di-irnine, tertiary baseand aliphatic acid anhydride required will vary from .one heterocyclicquaternary salt to another. The dehydrating agent, for example analiphatic acid anhydride,

may for instance be omitted entirely with advantage'in the;case ofbenzselenazolium salts, and the proportion of acid binding agent, such'as pyridine; to alicyclic diether, such as dioxan, may in this case andin the case pof some thiazolium salts be lowered with advantage to theextend of causing the reaction mixture to separate into two liquidphases. In the following examples, given by way of illustration only,the quaternary ammonium alkyl sulphate starting material was prepared ineach case by reacting the appropriate tertiary basewith an excessofalkyl sulphate; the crude reaction product so obtained and containingunreacted alkyl sulphate was used as such in the subsequent reaction:

Example I 63 gms. of 2z4z5-trimethylbenzoxazolium ethyl sulphate aredissolved by warming in a mixture of 12 ccs.

of pure dry pyridine, 30 ccs. f propionic anhydride, and

' 35 ccs. of pure dioxan. After standing for 3 hours, the

7 Example 2 V 90. gms. of 2-methyl-S-phnylbenzoxazolium ethyl sul- Vphate are dissolved by warming in a mixture of 12 ccs.

of pure dry pyridine, ccs. of acetic anhydrideand ccs. of pure dioxan.After-standing several hours the solution is boiled gently under refluxfor 2 /2 hours. It

is then. poured into 500 ccs. of ethanol and an equal 'volume of 20%aqueous ammonium thiocyanate is added, After standing several hours theliquors are de- 7 .boxylic acid anhydr'ide otherwise inert in thereaction andan "acid binding agent consisting of a tertiary or cantedand the residue worked 'up with ether till granu- V 1 lat. Theres-ultingdark red powder is recrystallized from 400 ccs. of methylacetoacetate. Ayield of 12 gms. of the sensitizer in the form of orange-red crystals isobtained. Optical characteristics; see Fig. 2.

Example 3 V V B 70r gms. of Z-methyLB-naphthiamlium methyl sulphate-aredissolved bywarming in a mixture of 40 ccs. of dioxan, 25 ccs. of puredry pyridine and 8 ccs. of acetic Zanhydride. :The solution is boiledgently under reflux for 16 hours and .th'en' poured into 500 ccs..ofethanol. T0 .theresulting ethanol solution 400 cos of a 20% aqueoussolution of sodium iodide are added with stirring, On standing,preferably overnight, green lustred crystals separate'whicharefilteredoff, washed with a mixture of alcohol and'ether (1:2), and-subsequentlyrecrystallized from methanol containing 10%i-6f its 7 volume of20%.isodiumiodideu yield of 110.5 gins,

of the sensitizer in the form of small lust-red crystals is obtained.Optical characteristics: see Fig. 3.

Example 4 80 gms. of 2-methyl-4:S-diphenylthiazolium ethyl sulphate aredissolved. by Warming ina mixture of ccs. of pure dioxane, 20 ccs. ofpyridine and 10 ccs. of acetic anhydride. The solution is boiled gentlyunder reflux for 24 hours. After. pouring into 500 ccs. of

ethanol, an equal volume of 20% aqueous sodiumiodide is added withstirring. On standing, preferably overnight, a crystalline deposit isformed which is filtered'off.

and washed with alcohol-ether (1:2). The dyestuff is recrystallized fromethanol to which 10% of its volume of 20% sodium iodide has been added.A yield of 12.5 gms. of a sensitizer in the form of dark violet crystalsis obtained. Optical characteristicsi see Fig. 4.

Example 5 54 gms. of lepidinemethyl sulphate is dissolved by warming ina mixture of.54 ccs. of pure dioxan, 15 ccs.

of pyridine and f6 ccs. of acetic anhydride. The .solu-V tion is thenboiled gently under reflux for 20 hours.

After. pouring it into 400005. of ethanol and adding an equal volume of20% aqueous sodium iodide, a fine de- 7 posit is thrown out onstanding'for at least 12 hours.-

The crystals are separated by filtration and recrystallized from ethanolcontaining. 20% "of its volume of 20% aqueous fsodiurn iodide. formingOptical characteristics: see Fig. 5. 7

Example 6 phate are treated with a mixture of 20 ccs. of" pure pyridineand'80 ccs. of pure dioxan. The mixture is boiled gently under refluxfor 16 hours and then'poured, into 400 ccs. of ethanol, On adding anequal volume of 20% aqueous sodium bromide, precipitation occurs 7 andthe reaction mixture is left standing overnight. The deposit istreated-first with alcohol-ether (1:2) and then washed with water. Thecrude product is recrystallized from methanol containing 10% of itsvolume of sodium iodide. A yield of 7-8 gms. of 'a sensitizer'in theform of lustrous crystals is obtained. Optical characteristics;

see Fig. 6.

I claim:

.1. A processfor the preparation of photographic sensitizers whichcomprises the step of reacting, in'the'presence of a dehydrating agentconsisting of a liquid car- .ganic 'base a quaternized heterocyclic basehaving at least .fiveand notmore than six atoms in the ringof which:atfleast one and not more than two are hetero' atoms'lselected from'thegroup consisting of nitrogen, oxygen, sulphurand selenium, at least oneof said hetero atoms being nitrogen, and a methyl substituted methinegroup in one 'of the' positions adjacent to and in the para position tothe qu'aternized' nitrogen atom of the base'with' a compound selectedfrom the group consistheterocyclic base ing of dioxan and piprazine;

2. A'process as claimed in claim in 'which the'conthe boiling point ofthe re densationis carried out .at action mixture. V

3. A process. asclaimed'in claim 1 in which said heterocyclic base is'qu'aterniied 2:4:5 trimethylbenzo'xazolr" 4. A process as claimed 'inclaim .1 "in which said quaternized'2 methyl '5 phenyl- 'benzoxazol. :1V

' SJA process as claimed in claim 1 in' which said heterocyclic base :is.quaternized Z-methyI-p-naphthiazoI. V

A small yield of a dyestufi' 'a blue violet. solution in alcohol isobtained,

64 gms. of 2- nethyl-benzs elenazolium methyl sul- 6. A process asclaimed in claim 1 in which said heterocyclic base is quaternized2-methy1-4z5-dipheny1- thiazol.

7. A process as claimed in claim 1 in which said heterocyclic base isquaternized Z-methyl-benzselenazol.

8. A process as claimed in claim 1 in which said compound is dioxan.

References Cited in the file of this patent

1. A PROCESS FOR THE PREPARATION OF PHOTOGRAPHIC SENSITIZERS WHICHCOMPRISES THE STEP OF REACTING IN THE PRESENCE OF A DEHYDRATING AGENTCONSISTING OF A LIQUID CARBOXYLIC ACID AHYDRIDE OTHERWISE INERT IN THEREACTION AND AN ACID BINDING AGENT CONSISTING OF A TERTIARY ORGANICBASE, A QUATERNIZED HETEROCYCLIC BASE HAVING AT LEAST FIVE AND NOT MORETHAN SIX ATOMS IN THE RING OF WHICH AT LEAST ONE AND NOT MORE THAN TWOARE HETERO ATOMS BEING NITROGEN, AND A METHYL SUBSTITUED METHINE OXYGEN,SULPHUR AND SELENIUM, AT LEAST ONE OF SAID HETERO ATOMS BEING NITROGEN,AND A METHYL SUBSTITUED METHINE GROUP IN ONE OF THE POSITIONS ADJACENTTO AND IN THE PARA POSITION TO THE QUATERNIZED NITROGEN ATOM OF THE BASEWITH A COMPOUND SELECTED FROM THE GROUP CONSISTING OF DIOXAN ANDPIPERAZINE.